Pure copper is rarely found in nature. Instead copper is usually combined with other elements in copper ores. Over a dozen copper ores are mined commercially around the world. Sulfide ores, in which copper is bonded to sulfur, are the most common. Other copper ores include oxide ores, carbonate ores, and mixed ores.
The processes for extracting copper from a copper ore varies according to the type of ore, the desired purity level of the final product, and other factors. Each process typically includes a series of steps during which unwanted components are removed physically, chemically and/or electrochemically, with the purity of copper increasing during the process. The first step often is the physical concentration of a copper ore into a copper concentrate, in which the level of copper can be increased from a few percent up to about 20% to 30%.
The extraction processes can be hydrometallurgical or pyrometallurgical. Hydrometallurgical processing of copper ores often results in incomplete recovery of copper and other precious metals, long cycle times, poor product quality, and the difficulty in disposal and/or treatment of reagents and by-products of the aqueous processes. Alternative copper extraction processes, particularly for refractory materials such as chalcopyrite or copper concentrates, can be conducted at high temperatures, under high pressure (e.g., an increased partial pressure of oxygen), and/or with strong chemical oxidants or expensive reagents.
Chalcopyrite (CuFeS2) is one of the most abundant copper-bearing minerals, which accounts for approximately 70 percent of the world's known copper reserves. For more than 30 years, a significant number of processes have been developed to leach copper from chalcopyrite. A number of demonstration plant operations have been conducted, but none of the processes have become completely commercially operational. During the past decades, there has been a decline in copper grades, often remarked upon as a future challenge to the copper industry. The decline in ore grades is projected to continue and, in addition, ore mineralogy would become more complex. The need to process low-grade and/or complex chalcopyrite-containing ores has been the main driver for the development of hydrometallurgical processes.
Thus, there is a need to improve the hydrometallurgical extraction of copper from copper ores and copper concentrates.